Cutting oil is a generic term for that class of oils which are used in metal machining operations. Cutting oil generally comprises one or more mineral oil, chlorinated or sulfurized mineral oil, fatty oil, or mixtures thereof. The cutting oil is provided at the cutting surface where a metal-shaping bit is used to modify a metal workpiece. Cutting oil provides a lubricating film between the cutting bit and the workpiece, thus keeping the cutting area cooled. The continuous flow of cutting oil acts to retain metal shards or flakes formed during the cutting process, and to carry these flakes away from the cutting surface. The cutting oil can also contain anti-corrosion agents, emulsifiers, anti-bacterial agents, and the like.
One example of a machining apparatus 110 is shown in FIG. 1. A workpiece 112 (shown in cross section) is supported below a cutting bit 114. The workpiece 112 and the cutting bit 114 are moved relative to one another, either by motion controls such as the handle means 116 shown, or by computer controls (not shown). Generally, motion controls provide relative movement along each of the x, y and z axis.
A reservoir of cutting oil is maintained within the body of the machining apparatus 110. The cutting oil is pumped to a nozzle 118 located proximal to the cutting surface. The cutting oil is sprayed over the workpiece 112 and the cutting bit 114. A drain system (not shown) returns the cutting oil to the reservoir.
The presence of metal flakes in the cutting oil has traditionally limited the effective use life of cutting oils. However, a variety of methods have been developed to enhance the life of the cutting oil by filtering the oil, either before it is sent to the cutting oil reservoir, while it is held within the reservoir, or as it is brought to the cutting surface. Generally, the larger flakes are removed by filtration or straining. The smaller metal flakes can be removed by skimming or other processes. Cutting oil can be filtered by the processes described in U.S. Pat. No. 4,325,663, for example.
Cutting oil can become contaminated by anaerobic bacteria. The presence of anaerobic bacteria in the cutting oil reservoir causes rank and rancid odors, limiting the useful life of the cutting oil for aesthetic reasons. The presence of the anaerobic bacteria can also provide a source of irritation or contagion for the humans who must come into contact with the cutting oil in either liquid or volatilized form.